1. Field of The Invention
Exemplary aspects of the present invention generally relate to a cleaning device and an image forming apparatus including the cleaning device.
2. Description of the Background
Related-art image forming apparatuses, such as copiers, printers, facsimile machines, and multifunction devices having two or more of copying, printing, and facsimile functions, typically form a toner image on a transfer member (e.g., a sheet of paper, etc.) according to image data using an electrophotographic method. In such a method, for example, a charger charges a surface of a photoconductor; an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet of transfer members; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
There is known an image forming apparatus including a cleaning device that electrostatically removes untransferred residual toner from an image carrier after transfer of a toner image from the image carrier onto a sheet. Specifically, the cleaning device includes a cleaning brush roller serving as a cleaning member that rotatably contacts the image carrier, a collection roller serving as a collection member that rotatably contacts the cleaning brush roller, and a scraping blade that contacts the collection roller. A cleaning voltage having a polarity opposite a normal charging polarity of toner is supplied to the cleaning brush roller. In addition, a collection voltage having the same polarity as and greater than the cleaning voltage is supplied to the collection roller. Untransferred toner remaining attached to the image carrier without being transferred onto the sheet is electrostatically moved from the image carrier to the cleaning brush roller by an electric field formed between the image carrier and the cleaning brush roller while being scraped off from the image carrier by the rotatable cleaning brush roller. The toner thus moved to the cleaning brush roller is further electrostatically moved to the collection roller, and then scraped off from the collection roller by the scraping blade.
In addition to the toner image, the image forming apparatus also forms a toner pattern for quality control at a predetermined timing. The toner pattern thus formed on the image carrier is detected by an optical sensor or the like. Image density of the formed toner pattern is then adjusted and color shift is corrected based on the detected result to achieve higher image quality. The toner pattern is also formed at an interval between sheets on the image carrier to replenish the developing device with new toner to achieve higher quality image. Subsequently, the above-described toner pattern formed on the image carrier for the purpose of providing higher quality image is simply removed from the image carrier by the cleaning device without being transferred onto the sheet.
However, although the toner patterns are reliably removed from the image carrier by the cleaning brush roller immediately after the toner patterns enter a contact position between the image carrier and the cleaning brush roller, the related-art cleaning device cannot reliably remove the toner patterns after a certain period of time elapses, causing irregular cleaning.